Although it is quite possible that many of the reported bio-chemical changes found in primary cancerous tissue and metastases may not be of etiological importance, it may be interesting to briefly refer to some of them as indicating the vital alteration in tissues connected with what we recognize as malignancy; even as in acute and chronic gout the affected tissues exhibit abnormal conditions in regard to uratic deposit. Many writers, some of them dating back many years, agree that albuminous constituents predominate in cancer tissue, and, as in actively growing structures in general, sugar forming substances abound. Wolter states that cancer of the breast contains 20 per cent. more nucleo-proteids than the normal breast. Casein is also present in breast cancers, and the abundance of fatty matters, contained in the cells of such neoplasms, is well known. In regard to the proteids, Wolff, after many studies, concludes that their character is identical with that of normal tissues, and it is only the quantitative distribution of these that differentiates the tumor from the physiological tissue. Wells agrees with others that there is no very distinctive character in the bio-chemistry of malignant tumors, but by reason of their excessive chemical component, as compared with benign tumors, they naturally show a high content of nuclear proteins; they, therefore, contain a high proportion of phosphorus and iron. Interesting observations have also been made on other characteristics of cancerous tissues, such as the great abundance of enzymes of great variety which are actively autolytic, also in regard to certain relations of cholesterin, in regard to which Ewing has recently said, “There appears to be something in the chemical or mechanical nature of the irritation of cholesterin which is peculiarly effective in producing atypical proliferation of epithelium”; this has been found to be no less than 65 per cent. greater in quantity in fatty deposits, as in the mesentery, in subjects of cancer than in healthy persons, etc., etc. It would weary you to no purpose to attempt to refer further to the bewildering mass of research studies in connection with the bio-chemistry of cancer which are found in special literature: much of it is fragmentary and some of it contradictory, but all has its value as contributory to our knowledge of the actual conditions developed in connection with cancer growth; but up to the present time it cannot be claimed that any very practical results have been thus attained which will aid us in treating the disease.